Heat exchanger



Fel '5, 1963 H. J. coLEs x-:TAL I- 3,076,443

HEAT EXCHANGER u Filed June 17, 1959 3 Smeets-Sheerl 1 /ZQ .I

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Feb. 5, 1963 Filed June 17. 1959 H. J. COLES ETAL HEAT EXCHANGER 5 Sheets-Sheet 2 Feb. 5, 1963 H. J. coLEs x-:TAL

HEAT EXCHANGER 5 Sheets-Sheet 3 Filed June 17, 1959 i fafa/mu M2M/WJ* 5.44 J

United States Patent HEAT EXCHANGER Harold .lohn Coles and John Machintosh Sutherland, London, England, assignors to Mitchell Engineering Limited, London, England, a company of Great Britain Filed lune 17, 1959, Ser. No. 820,941

Claims priority, application Great Britain lune 19, 1958 3 Claims. (Cl. 122-34) This invention relates to heat exchangers.

According to the present invention a heat'exchanger comprises a lower casing and a lirst tube plate secured to the upper end of the casing to define therewith a closed chamber, said chamber having an inlet thereto and an outlet therefrom for one of the media between which heat exchange is to be effected, a plurality of first tubes sealed in holes in the tube plate and extending downwardly towards the lower end of the casing, said first tub-es opening at their upper ends to above the tube plate and being closed at their lower ends, a second tube plate mounted above the first tube plate in spaced relation thereto, a plurality of second tubes sealed in holes inthe second tube plate and extending downwardly therefrom coaxially into the iirst tubes to adjacent their lower ends, each second tube being open at each end, and means to deliver a second of the media between which heat exchange is to be effected, to the upper ends of the second tubes and to receive the media from the upper ends of the iirst tubes.

p .The second medium receives heat principally while it is in the first tubes (that is, in the annular space surrounding the second tubes), through the walls of the first tubes, and, presuming it to have a positive coeflicient of thermal expansion or that substantial vaporization occurs a circulation is promoted or generated downwardly through the second tubes and upwardly in the spaces l medium is radioactive after passing through the reactor.

In this circumstance, it is desirable that the heat-exchanger be mounted so that parts to which the radioactive primary heat-transfer medium has access are located within a shielding wall surrounding the reactor against escape of radiation. exposed to radioactive material have to be constructed of, or at least their surfaces clad in stainless steel, which has a coeiicient of thermal expansion different from materials such as mild steel which are conveniently used for structural members, are lessened since the tubes are suspended by one end from the tube plates thus enabling them to expand and contract freely, independently of any expansion of the casing.

A preferred embodiment of the invention is adapted for use where the primary heat transfer medium is steam generated, for example, by a boiling Water reactor, and the secondary heat transfer medium is also steam (or water).

In one arrangement suitable for this use, the means to deliver and receive the second medium comprises an upper casing secured to the first tube plate and forming therewith a second chamber enclosing the second tube plate, a cylindrical baille within the second chamber in spaced relation to the upper casing and extending upwardly from the periphery of the second tube plate to form a well, a liquid supply pipe delivering the liquid into the well, an outlet from the upper end of the chamber for the vaporised liquid, said outlet communicating with the open ends of the first tubes through the space between the tube plates and the space between the cylindrical bale and the upper casing, and baille means in Also difliculties due to the fact that parts I Mice the dow path of the vaporised liquid from said space between the cylindrical baffle and the upper casing and said outlet from the second chamber.

According to a feature of the invention, the vpath of the primary steam may include passage through a catalyst such as active platinized material capable of recombining free oxygen and hydrogen in the primary steam produced by dissociation under the action of high-energy particles or radiation in the reactor. y Such catalyst may be provided in one or more beds located within an annular space between the casing and a baille member directing the primary steam as described to the upper part of the chamber.

In a construction in which steam is used as the secondary heat-transfer medium, such medium may be fed as water on to the top of the second (upper) tube plate, whence it can pass down the inner tubes. Steam generated from this water as it passes up the outer tubes may, after emerging from the tops of the outer tubes, be conducted to a steam-water separator for drying purposes. Preferably, such a separator is housed above the upper tube plate whereby condensate from the separator joins the feed water to the exchanger tubes, and dry steam is led ofi, for example, to a turbine.

The lower ends of the outer tubes may each be sealed ofi separately, or they may lead into a common header which is free to move with the tubes and independently of the casing surrounding the same.

One specific form of heat exchanger embodying this invention will now be described with reference to the accompanying drawings, in which:

FIGURES 1A, 1B together form a vertical crosssection through the heat exchanger, the figures being joined on the line 1 1, Y

FIGURE 2 is part of FIGURES 1A, 1B drawn to a larger scale, and

FIGURE 3 is a section on the line 3-3 of FIG- URE lA. p

The heat exchanger illustrated is suitable for generating steam from water, by heat exchange with steam which has been produced in cooling a nuclear reactor.

The heat exchanger comprises a lower casing 10 of mildy steel having a stainless steel lining 11, and an uppercasing 12 also of mild steel. Each casing comprises4 a domed end portion 10a, 12a, a cylindrical centre portion 10b, 12b and a bolting flange portion 10c, 12C, the portions of each casing 10, 12 being welded together as indicated at 13.

The two casings 1i), 12 are disposed with their bolting flanges 10c, 12C adjacent and a tube 14 is sandwiched between the two casings, the casings 10, 12 and plate 14 being secured together by a ring of studs 15 receiving nuts 16.

The tube plate A14 is formed with a large number of tube-receiving holes into which project the upper ends of stainless steel tubes 17. The tubes 17 are brazed or welded in position in the holes with their upper ends flush with the upper surface of the tube plate `1d (FIGURES 1B, 2) and they project downwardly to adjacent the bottom of lower end of the cylindrical portion 10b of the casing 10. The upper ends of the tubes 17 are open and their lower ends are closed so that the bores of the tubes are only in communication with the interior of casing 12.

The tubes 17 are surrounded by a cylindrical bafiie 18 which is held in position in spaced relation to the casing by a channel section ring 19 secured to the casing lil and the baffle 18 at about the mid length of the baille. The ends of the battle 18 are spaced from the plate 14 and from the end portion 10a.

A primary steam inlet pipe 20 is secured in the casing portion 10b just above the ring 19 to open to the space 21 between the casing 10 and baille 1S, and this space also accommodates, above the ring 19, a series of catalyst beds 22 which consist for example oi platinized granular material. Any dissociated hydrogen and oxygen in the entering steam is recombined in passing through the catalyst beds 22. The domed end a has iitted in it a condensate outlet pipe 23.

The space within the upper casing 12 houses a cylindrical baille 24 (FIGURE 1A) which extends upwardly from the tube plate 14 part way along the length of the casing. The baille 24 has an upper tube plate 25 mounted in it at a short distance above its lower end, and the plate 25 has in it a series of holes aligned with the tubes 17, each hole having iitted in it an open ended tube 26 whereof the upper end is vilush with the top 'surface of the plate 25 and which projects downwardly-into Vthe aligned tube 17 to adjacent its lower end (FIGURE 2). The baille 24 and `plate y25'together provide a wellfZS into which water is fed from a 'perforated'end portion 29 (FIGURE 3) of a water supply pipe 30mounted in the end portion 12a of the casing 12. The space 39 below the plate 25 communicates through cutaways 40 in the lbaille 24 with annular space 31 between the baille 24Yand the casing 12.

`An annular baille 32 is secured'to the casing-12'above the upper end of the baille 24'and'the inner edge of the baflle-32 is downturned to project into the upperend'of the baille 24 in spaced relation thereto.

The baille 24 has a-series of rings of circumferentially disposed holes 33 in it above the level of the perforated pipe portion 29 and each of these holes is'provided internally of the baille 24 with a downwardly open shroud 34.

The end portion `12a of the upper casing '12 has an outlet pipe'35 ilttedin it, the pipe Vprojecting downwardly into the larger diameter portion of a'funnel member 37, there being a ring'of swirl vanes 36'supported in the'annular space between the pipe 35 andthe funnel member 37, the lower delivery portion 37a Vof which is of"small bore-and extends downwardly to adjacent the portion 29 of the water inlet pipe 30.

In operation, the primary steam, which maybe wet, dry or superheated steam, is `fed to pipe 20 and`itilows upwardly through space'21 and the catalyst beds 22`where any dissociated hydrogen and oxygen ar'e recombined, and then tlows downwardly within the baille 18 vover the external surfaces of the tubes 17'to heat the secondary iluid ilowing in these tubes. The steam is condensed and the condensate leaves the casing lothrough'outlet'pipe 23.

The secondary iluid, which is feed-water whichis to be converted to steam, is fed through pipes'29, 30 into the well 28 at such a rate that the water level inthe well is maintained below the holes 33 but above'thepipe-portion 29 and the lower end of the portion 37a of the lfunnel member 37. The water ilows from the'well 28 downwardly through pipes '26 and'then upwardly through the annular spaces between the tubes 26, 17 and is thereby heated and vaporised. The steamgenerated in the tubes 26, 17 Vrises more rapidly than any water in the spaces between the tubes 17, 26 and the steam ilows from ythe tubes 17 into space 39 through cutaways 4i) into space 31, and then ilows'from the' space 31 around the annular baille 32 and through the holes `33 into the upper part of the casing 12. Thebaille 32 and shrouded holes 33 act to separate any water from the rising steam, and any water so separated is returned to the ywell A28 to be recirculated throughthetubes 17, 26. The steam then ilows to the outlet pipe 35 through the swirl vanes 36 and any water remaining in the steam is'separated out and ilows down through the funnel member 37 into the well 28.

We claim: A

l. A heat exchanger wherein a liquid is vaporized by heat exchange with a hot VViluid medium, comprising a lower casing having a closed lower end, an upper casing' having a closed upper end, a iirst tube plate secured be tween and separating the casings to deilne therewith lower and upper closed chambers, the lower chamber having an inlet thereto and an outlet therefrom for the iluid medium, a plurality of ilrst tubes sealed in holes in the tube plate and extending downwardly towards the lower end of the lower chamber, said iirst tubes being open at their upper ends to the upper chamber and being closed at their lower ends, a second tube plate mounted within the upper chamber above and in spaced relation to the ilrst tube plate, said Vsecond tube plate having its periphery spaced from the upper casing, a plurality of second tubes sealed yin holes in the second tube plate and extending downwardly therefrom coaxially into the lirst tubes to adjacent their lower ends, each second tube being open at each end, a

cylindrical baille accommodated within the upper chamlber and extending upwardly from the periphery of the second tube plate in spaced relation to the upper casing, said cylindrical baille and said second tube plate together vdefining a Well, said cylindrical baille vhaving an upper edge spaced vertically away from the upper end of the upper casing, a liquid supply pipe having an outlet delivering the liquid into the well at a level substantially below said upper-edge of the cylindrical baille, an outlet .from the upper end of the upper casing for the vaporized liquid, said outlet communicating with the open ends of theiirst tubes through the space between the first and second tube plates and the space between the cylindrical baille and the upper casing, and an annular baille secured 'totheupper casing at a level above said upper edge of the cylindrical baille, the annular baille extending inwardly'beyond said upper edge and having a downturned Vinner edge portion projecting into the well to a level between said outlet of the liquid supply pipe and the upper `edge of'the cylindrical baille.

2. A heat exchanger according to claim 1, the cylin- 'drical baille having therein a circum'ferentially disposed Vseries ofholes, the holes being above the level of the said outlet of the liquid supply pipe, and said cylindrical -baille also having projecting from it inwardly into the Wella corresponding series of downwardly-open shrouds,

`one for each of the holes.

3. A-heatv exchanger as claimed in claim 1, the outlet 'from the upper chamber comprising a pipe projecting downwardly from the upper end of the upper'casing and open at its upper end, and there being a funnel member having a large diameter upper portion surrounding the pipe in spaced relation thereto and a small bore delivery portion extending downwardly into the well to adjacent the outlet of the liquid supply pipe, and a ring of swirl vanes accommodated within the space between the outlet pipe and the large diameterupper portion of the funnel member.

References Cited in the ille of this patent UNITED STATES PATENTS 

1. A HEAT EXCHANGER WHEREIN A LIQUID IS VAPORIZED BY HEAT EXCHANGE WITH A HOT FLUID MEDIUM, COMPRISING A LOWER CASING HAVING A CLOSED LOWER END, AN UPPER CASING HAVING A CLOSED UPPER END, A FIRST TUBE PLATE SECURED BETWEEN AND SEPARATING THE CASINGS TO DEFINE THEREWITH LOWER AND UPPER CLOSED CHAMBERS, THE LOWER CHAMBER HAVING AN INLET THERETO AND AN OUTLET THEREFROM FOR THE FLUID MEDIUM, A PLURALITY OF FIRST TUBES SEALED IN HOLES IN THE TUBE PLATE AND EXTENDING DOWNWARDLY TOWARDS THE LOWER END OF THE LOWER CHAMBER, SAID FIRST TUBES BEING OPEN AT THEIR UPPER ENDS TO THE UPPER CHAMBER AND BEING CLOSED AT THEIR LOWER ENDS, A SECOND TUBE PLATE MOUNTED WITHIN THE UPPER CHAMBER ABOVE AND IN SPACED RELATION TO THE FIRST TUBE PLATE, SAID SECOND TUBE PLATE HAVING ITS PERIPHERY SPACED FROM THE UPPER CASING, A PLURALITY OF SECOND TUBES SEALED IN HOLES IN THE SECOND TUBE PLATE AND EXTENDING DOWNWARDLY THEREFROM COAXIALLY INTO THE FIRST TUBES TO ADJACENT THEIR LOWER ENDS, EACH SECOND TUBE BEING OPEN AT EACH END, A CYLINDRICAL BAFFLE ACCOMMODATED WITHIN THE UPPER CHAMBER AND EXTENDING UPWARDLY FROM THE PERIPHERY OF THE SECOND TUBE PLATE IN SPACED RELATION TO THE UPPER CASING, SAID CYLINDRICAL BAFFLE AND SAID SECOND TUBE PLATE TOGETHER DEFINING A WELL, SAID CYLINDRICAL BAFFLE HAVING AN UPPER EDGE SPACED VERTICALLY AWAY FROM THE UPPER END OF THE UPPER CASING, A LIQUID SUPPLY PIPE HAVING AN OUTLET DELIVERING THE LIQUID INTO THE WELL AT A LEVEL SUBSTANTIALLY 